Variable clearance mechanism for use in a turbine engine and method of assembly

ABSTRACT

A variable clearance mechanism for use in a turbine engine is provided that includes a stationary component, a plurality of articulating seal members coupled to the stationary component, and a biasing mechanism including an actuation ring. The variable clearance mechanism varies the position of stationary seal members to provide variable bucket tip clearance as a function of an operating condition of the turbine engine. The biasing mechanism is coupled to the plurality of articulating seal members for use in selectively translating the plurality of articulating seal members when the actuation ring is rotated circumferentially relative to the stationary component.

BACKGROUND

The field of the present disclosure relates generally to turbine engines and, more specifically, to a variable clearance mechanism that includes articulating seal members for use in a turbine engine.

Known turbines experience several different phases of operation including, but not limited to, start-up, warm-up, steady-state, shutdown, and cool-down. In at least some of such known turbines, clearances between turbine rotor blade tips and inner surfaces of the surrounding seal members are controlled to facilitate improving operating efficiency. Such clearances generally vary as the turbine transitions from one operational phase to another. More particularly, each operational phase has different operating conditions associated with it, such as temperature, pressure, and rotational speed, which will induce changes in the clearances between turbine components, including static and moving components within the turbine.

In at least some known turbines, the clearances between the turbine rotor blades and the seal members are also controlled to prevent contact-related damage therebetween as the turbine transitions between operational phases. For example, in at least some known turbines, cold, or assembly, clearances are set to be no larger than required for steady-state operation to account for thermal and mechanical differences in the turbine when transitioning between phases of operation. Moreover, as described above, turbine efficiency depends at least in part on the clearance between tips of the rotating blades and seal members coupled to the surrounding casing. If the clearance is too large, enhanced gas flow may unnecessarily leak through the clearance gaps, thus decreasing the turbine's efficiency.

At least some known turbines use abradable and/or labyrinth seals that facilitate reducing leakage flow through the clearance gap. The leakage flow adversely affects turbine performance by bypassing flow around the blades that could be used to provide useful output for the turbine. Moreover, at least some known turbines facilitate reducing operating clearances by forming components from materials having a relatively low coefficient of thermal expansion, and/or with active translation of moveable seal members.

BRIEF DESCRIPTION

In one aspect of the disclosure, a variable clearance mechanism for use in a turbine engine is provided. The mechanism includes a stationary component, a plurality of articulating seal members coupled to the stationary component, and a biasing mechanism including an actuation ring. The biasing mechanism is coupled to the plurality of articulating seal members for use in selectively translating the plurality of articulating seal members when the actuation ring is rotated circumferentially relative to the stationary component.

In another aspect of the disclosure, a turbine engine is provided. The turbine engine includes a rotor blade assembly including a plurality of rotor blades, a stationary component, a plurality of articulating seal members coupled to the stationary component, and a biasing mechanism including an actuation ring. The biasing mechanism is coupled to the plurality of articulating seal members for use in selectively translating the plurality of articulating seal members when the actuation ring is rotated circumferentially relative to the stationary component.

In yet another aspect of the disclosure, a method of assembling a variable clearance mechanism for use in a turbine engine is provided. The method includes providing a stationary component, coupling a plurality of articulating seal members to the stationary component, and coupling an actuation ring to the plurality of articulating seal members such that the actuation ring is configured to selectively translate the plurality of articulating seal members when the actuation ring is rotated circumferentially relative to the stationary component.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic illustration of an exemplary steam turbine engine.

FIG. 2 is an enlarged view of an exemplary turbine rotor blade that may be used in the turbine engine shown in FIG. 1.

FIG. 3 is an axial view of an exemplary variable clearance mechanism that may be used in the turbine engine shown in FIG. 1 and in a first operational position.

FIG. 4 is an enlarged axial view of the variable clearance mechanism shown in FIG. 3.

FIG. 5 is an axial view of the variable clearance mechanism shown in FIG. 3 and in a second operational position.

FIG. 6 is an axial view of an alternative variable clearance mechanism that may be used in the turbine engine shown in FIG. 1.

FIG. 7 is an axial view of a further alternative variable clearance mechanism.

DETAILED DESCRIPTION

Embodiments of the present disclosure relate to systems and methods for use in controlling blade tip clearance in a turbine engine. More specifically, the systems described herein include articulating seal members that are easily configured to accommodate variations in the blade tip clearance during transient and/or steady-state operational phases of the turbine engine. The articulating seal members are coupled to a biasing mechanism that selectively translates the seal members radially during transitions between the transient and steady-state operational phases. The biasing mechanism includes an actuation ring and a plurality of levers coupled, either directly or indirectly, between the actuation ring and the seal members. As the actuation ring rotates circumferentially, the levers convert the circumferential motion of the actuation ring to a radial motion induced to the seal members. As such, the blade tip clearance may be selectively controlled to facilitate maintaining the integrity of the blade tips and seal members to improve the efficiency of the turbine engine.

As used herein, the terms “axial” and “axially” refer to directions and orientations that extend substantially parallel to a longitudinal axis of a turbine engine. Moreover, the terms “radial” and “radially” refer to directions and orientations that extend substantially perpendicular to the longitudinal axis of the turbine engine. In addition, as used herein, the terms “circumferential” and “circumferentially” refer to directions and orientations that extend arcuately about the longitudinal axis of the turbine engine. It should also be appreciated that the term “fluid” as used herein includes any medium or material that flows, including, but not limited to, air, gas, liquid and steam.

FIG. 1 is a schematic view of an exemplary steam turbine engine 10. While FIG. 1 describes an exemplary steam turbine engine, it should be noted that the variable clearance mechanism and methods described herein are not limited to any one particular type of turbine engine. One of ordinary skill in the art should appreciate that the variable clearance mechanism and methods described herein may be used with any rotary machine, including a gas turbine engine, in any suitable configuration that enables such an apparatus, system, and method to operate as further described herein.

In the exemplary embodiment, turbine engine 10 is a single-flow steam turbine engine. Alternatively, turbine engine 10 may be any type of steam turbine, such as, without limitation, a low-pressure turbine engine, an opposed-flow high-pressure and intermediate-pressure steam turbine combination, a double-flow steam turbine engine, and/or other steam turbine types. Moreover, as discussed above, the present invention is not limited to only being used in steam turbine engines and can be used in other turbine systems, such as gas turbine engines.

In the exemplary embodiment shown in FIG. 1, turbine engine 10 includes a plurality of turbine stages 12 that are coupled to a rotatable shaft 14. A casing 16 is divided longitudinally into an upper half section 18 and a lower half section (not shown). Upper half section 18 includes a high pressure (HP) inlet 20 and a low pressure (LP) outlet 22. Shaft 14 extends through casing 16 along a centerline axis 24, and is supported by bearings (not shown) at a journal 30. End packings 26 and 28 facilitate restricting operating fluid from escaping casing 16.

In the exemplary embodiment, turbine engine 10 also includes a stator component 44 coupled to casing 16. Casing 16 and stator component 44 each extend circumferentially about shaft 14. Shaft 14 includes a plurality of turbine stages 12 through which high-pressure, high-temperature operating fluid 40 is passed via turbine inlet 46. Turbine stages 12 include a plurality of nozzles 48. Turbine engine 10 may include any number of nozzles 48 that enables turbine engine 10 to operate as described herein. For example, turbine engine 10 may include more or less nozzles 48 than are illustrated in FIG. 1. Turbine stages 12 also include a plurality of rotor blades 38. Turbine engine 10 may include any number of rotor blades 38 that enables turbine engine 10 to operate as described herein. Operating fluid 40 enters turbine inlet 46 through HP inlet 20 and flows along shaft 14 through turbine stages 12, and exiting through outlet 22.

During operation, high pressure and high temperature operating fluid 40 is channeled to turbine stages 12 from an energy source, such as a boiler (not shown), wherein thermal energy is converted to mechanical rotational energy by turbine stages 12. More specifically, operating fluid 40 is channeled through casing 16 from HP inlet 20 where it impacts the plurality of rotor blades 38, coupled to shaft 14 to induce rotation of shaft 14 about centerline axis 24. Operating fluid 40 exits casing 16 at LP outlet 22. Operating fluid 40 may then be channeled to the boiler (not shown) where it may be reheated or channeled to other components of the system, e.g., a condenser (not shown).

FIG. 2 is an enlarged view of an exemplary turbine stage 12 that may be used in turbine engine 10 shown in FIG. 1. In the exemplary embodiment, turbine stage 12 includes nozzle 48 and rotor blade 38 that includes an airfoil 27 and a dovetail 29, which is coupled to a rotor disk 33. Rotor disk 33 is coupled to rotate with shaft 14 (shown in FIG. 1). Each nozzle 48 includes a vane 17 coupled to a first stationary component 19 and to a second stationary component 21 within casing 16 (shown in FIG. 1). Each vane 17 remains stationary relative to shaft 14. An exemplary clearance 23 is defined between a tip 25 of airfoil 27 and an articulating seal member 104. Components such as casing 16, components 19 and 21, vane 17 and airfoil 27 expand when heated as turbine engine 10 transitions between a transient operational phase (for example, a start-up phase and a warm-up phase) and a steady-state operational phase. As a result, clearance 23 will vary as turbine engine transitions between different turbine operational phases. Clearance 23 may will also vary as a result from other operational factors such as vibrational forces, bearing oil film thickness, and/or bearing alignment.

In the exemplary embodiment, turbine engine 10 also includes a variable clearance mechanism 100. Variable clearance mechanism 100 includes a biasing mechanism 102 and articulating seal member 104 coupled to biasing mechanism 102. Biasing mechanism 102 selectively translates articulating seal member 104 to facilitate modifying clearance 23 as turbine engine 10 transitions between a transient operational phase and a steady-state operational phase.

FIG. 3 is an axial view of variable clearance mechanism 100 that may be used in turbine engine 10 (shown in FIG. 1) in a first operational position 106, FIG. 4 is an enlarged axial view of variable clearance mechanism 100, and FIG. 5 is an axial view of variable clearance mechanism 100 in a second operational position 108. In the exemplary embodiment, variable clearance mechanism 100 includes first stationary component 19, a plurality of articulating seal members 104 positioned radially inward from first stationary component 19, and biasing mechanism 102 that selectively translates articulating seal members 104 generally radially during operation. Biasing mechanism 102 includes an actuation ring 110 that is radially outward from first stationary component 19 and that is coupled, either directly or indirectly, to articulating seal members 104. Alternatively, actuation ring 110 is located relative to stationary component 19 at any position that enables biasing mechanism 102 to function as described herein. At least one lever 112 is coupled to actuation ring 110, first stationary component 19, and at least one articulating seal member 104. Actuation ring 110 extends about first stationary component 19 at any length that enables variable clearance mechanism 100 to function as described herein. For example, actuation ring 110 may extend between about 0 degrees and about 360 degrees about centerline axis 24 of turbine engine 10. Moreover, actuation ring 110 remains a substantially uniform circumferential distance from first stationary component 19 as actuation ring 110 is rotated.

Biasing mechanism 102 also includes an actuator 114 coupled to actuation ring 110. Actuator 114 may be any device that induces circumferential rotation to actuation ring 110 during operation. For example, exemplary actuators may include, but are not limited to, a motor-driven device, a hydraulic device, and a pneumatic device. In the exemplary embodiment, actuator 114 includes a casing 116 and a piston 118 selectively translatable within casing 116. Piston 118 is coupled to actuation ring 110 via a pivot point 120. In operation, piston 118 selectively translates generally linearly within casing 116, and pivot point 120 converts the linear motion of piston 118 into a circumferential rotation of actuation ring 110.

Referring to FIG. 3, turbine engine 10 is in a transient operational phase. During the transient operational phase, components of turbine engine 10 are in thermal and vibrational flux, which may result in variations in clearance 23 between tip 25 of airfoil 27 (each shown in FIG. 2) and first stationary component 19. Such flux is caused by at least one of varying expansion and/or contraction of components of turbine engine 10 due to differing rates of thermal expansion as such components may be formed from different materials, varying thermal gradients within each component, and/or a vibratory response caused by rotor imbalance. As such, in the exemplary embodiment, variable clearance mechanism 100 is in first operational position 106 when turbine engine 10 is in a transient operational phase. More specifically, variable clearance mechanism 100 translates articulating seal members 104 radially outward to accommodate variations in clearance 23 and to facilitate reducing contact and abrasion between tip 25 and articulating seal members 104.

In the exemplary embodiment, articulating seal members 104 are translated radially outward by rotating actuation ring 110 in a first circumferential direction 122. More specifically, articulating seal members 104 are coupled to actuation ring 110 such that rotation of actuation ring 110 in first circumferential direction 122 facilitates increasing clearance 23 and increasing a gap 124 formed between adjacent articulating seal members 104. Actuation ring 110 may be rotated in first circumferential direction 122 by any circumferential amount that enables variable clearance mechanism 100 to function as described herein. As such, clearance 23 is selected as a function of a degree of circumferential rotation of actuation ring 110. Moreover, levers 112 are coupled between actuation ring 110 and each articulating seal member 104 to enable articulating seal members 104 to selectively translate simultaneously as actuation ring 110 is rotated.

Referring to FIG. 4, levers 112 are coupled to actuation ring 110, first stationary component 19, and articulating seal members 104 such that rotation of actuation ring 110 is converted into radial movement of articulating seal members 104. More specifically, levers 112 enable actuation ring 110 to selectively translate articulating seal members 104 radially without expanding and/or contracting radially itself. In the exemplary embodiment, each lever 112 includes a first end 126, an opposing second end 128, and a middle portion 130 extending therebetween. First end 126 is coupled to actuation ring 110, middle portion 130 is coupled to first stationary component 19, and second end 128 is coupled to articulating seal member 104 via a series of pins 132. During operation, lever 112 rotates about middle portion 130 as actuation ring 110 rotates circumferentially. As such, the coupling at middle portion 130 defines a fixed pivot point, and the couplings at first and second ends 126 and 128 each define moving pivot points. More specifically, in the exemplary embodiment, slots 134 are defined in each of first and second ends 126 and 128 to enable sliding engagement between pins 132 and slots 134. As such, the sliding engagement between pins 132 and slots 134 facilitates accommodating any radial mismatch between a length L of lever 112 and a distance D defined between actuation ring 110 and articulating seal members 104.

In the exemplary embodiment, biasing mechanism 102 includes a biasing element 135 that facilitates ensuring articulating seal members 104 are biased in a radially inward direction as turbine engine 10 (shown in FIG. 1) transitions between operational phases. More specifically, as the circumferential movement of actuation ring 110 causes articulating seal members 104 to translate substantially linearly, a lag between the movement of actuation ring 110 and the movement of articulating seal members 104 may be caused by the sliding engagement between pins 132 and slots 134 in levers 112. As such, in the exemplary embodiment, biasing element 135 is coupled between articulating seal members 104 and lever 112 to ensure the sliding engagement between pins 132 and slots 134 is responsive to the circumferential rotation of actuation ring 110. Alternatively, biasing element 135 may be coupled between articulating seal members 104 and any suitable component that enables biasing mechanism 102 to function as described herein. An exemplary biasing element 135 includes, but is not limited to, a spring.

Referring to FIG. 5, turbine engine 10 is in a steady-state operational phase. During steady-state operations, components of turbine engine 10 reach substantial thermal equilibrium such that clearance 23 between tip 25 and articulating seal members 104 remains substantially uniform during operation. In the exemplary embodiment, variable clearance mechanism 100 remains in second operational position 108 when turbine engine 10 is in a steady-state operational phase. More specifically, variable clearance mechanism 100 translates articulating seal members 104 radially inward to facilitate decreasing clearance 23, to facilitate reducing fluid leakage through clearance 23, and thus to facilitate increasing the efficiency of turbine 10.

In the exemplary embodiment, articulating seal members 104 are translated radially inward by rotating actuation ring 110 in a second circumferential direction 136. More specifically, articulating seal members 104 are coupled to actuation ring 110 such that rotating actuation ring 110 in second circumferential direction 136 facilitates decreasing clearance 23 and reducing gap 124 (shown in FIG. 3) defined between adjacent articulating seal members 104. Actuation ring 110 is rotated in second circumferential direction 136 to any angular distance that enables variable clearance mechanism 100 to function as described herein. As such, clearance 23 is selected as a function of a degree of circumferential rotation of actuation ring 110. Moreover, as described above, levers 112 are coupled between actuation ring 110 and each articulating seal member 104 such that articulating seal members 104 selectively translate simultaneously when actuation ring 110 is rotated circumferentially.

FIG. 6 is an axial view of an alternative variable clearance mechanism 200. In the exemplary embodiment, variable clearance mechanism 200 includes a rack and pinion assembly 138 coupled between actuation ring 110 and stationary component 19 that facilitates translating seal members 104 in response to rotation of actuation ring 110 relative to first stationary component 19. Rack and pinion assembly 138 includes a plurality of pinions 140 coupled to and spaced circumferentially about first stationary component 19, and a toothed rack 142 defined on an inner radial portion 144 of actuation ring 110. Levers 112 are coupled to pinions 140 such that rotation of pinions 140 selectively translates articulating seal members 104 substantially radially. When actuator 114 induces circumferential rotation to actuation ring 110, toothed rack 142 engages and rotates pinions 140. As such, clearance 23 is selected as a function of a degree of rotation of pinions 140.

FIG. 7 is an axial view of an alternative variable clearance mechanism 300. In the exemplary embodiment, variable clearance mechanism 300 includes a slide track 145 coupled between adjacent articulating seal members 104 and lever 112 coupled to slide track 145. Slide track 145 facilitates maintaining alignment between adjacent articulating seal members 104 as they selectively translate substantially radially during operation of variable clearance mechanism 300. For example, articulating seal members 104 translate circumferentially along slide track 145 as articulating seal members 104 selectively translate substantially radially. First stationary component 19 (shown in FIG. 2) includes slots 146 formed therein to facilitate sliding engagement between pins 132 and slots 146. As such, the sliding engagement between pins 132 and slots 146 facilitates accommodating for the radial mismatch between length L of lever 112 and distance D (shown in FIG. 4) between actuation ring 110 and seal members 104. Moreover, in the exemplary embodiment, only one lever 112 is coupled between actuation ring 110 and slide track 145 to facilitate translating seal members 104 radially.

The systems and methods described herein facilitate clearance control between a rotor assembly and adjustable seal members in a turbine engine. More specifically, the variable clearance mechanism described herein includes a biasing mechanism that selectively translates the adjustable seal members radially to modify a clearance between the rotor assembly and the seal members while closing a clearance between adjacent seal members. The biasing mechanism includes an actuation ring coupled to the seal members with a system of levers. The levers facilitate selectively translating the seal members radially as the actuation ring rotates circumferentially. By actuating the seal members with the circumferential rotation of the actuation ring, the biasing mechanism is not limited by radial movement constraints defined by the casing of the turbine, and can be actuated with a single mechanism. As such, the variable clearance mechanism facilitates selectively modifying the clearance between the rotor assembly and the adjustable seal members as the turbine engine transitions between operational phases.

This written description uses examples to disclose the invention, including the best mode, and also to enable any person skilled in the art to practice the invention, including making and using any devices or systems and performing any incorporated methods. The patentable scope of the invention is defined by the claims, and may include other examples that occur to those skilled in the art. Such other examples are intended to be within the scope of the claims if they have structural elements that do not differ from the literal language of the claims, or if they include equivalent structural elements with insubstantial differences from the literal languages of the claims. 

What is claimed is:
 1. A variable clearance mechanism for use in a turbine engine, said mechanism comprising: a stationary component; a plurality of articulating seal members coupled to said stationary component; and a biasing mechanism comprising an actuation ring, said biasing mechanism coupled to said plurality of articulating seal members for use in selectively translating said plurality of articulating seal members when said actuation ring is rotated circumferentially relative to said stationary component.
 2. The mechanism in accordance with claim 1, wherein said actuation ring is rotated in a first circumferential direction to translate said plurality of articulating seal members radially inward, and said actuation ring is rotated in a second circumferential direction to translate said plurality of articulating seal members radially outward.
 3. The mechanism in accordance with claim 2, wherein a degree of translation of said plurality of articulating seal members is selected based on a degree of rotation of said actuation ring in the first and second circumferential directions.
 4. The mechanism in accordance with claim 1, wherein said biasing mechanism comprises at least one lever coupled between said actuation ring and at least one of said plurality of articulating seal members, wherein said at least one lever is configured to convert circumferential movement of said actuation ring into substantially linear movement of said plurality of articulating seal members.
 5. The mechanism in accordance with claim 4, wherein said biasing mechanism comprises at least one lever coupled between said actuation ring and each of said plurality of articulating seal members such that said plurality of articulating seal members are simultaneously translated when said actuation ring is rotated circumferentially.
 6. The mechanism in accordance with claim 1, wherein said biasing mechanism comprises an actuator coupled to said actuation ring, said actuator configured to induce circumferential rotation to said actuation ring.
 7. The mechanism in accordance with claim 1, wherein said actuation ring is configured to remain at a substantially uniform distance from said stationary component as said actuation ring rotates circumferentially.
 8. A turbine engine comprising: a rotor blade assembly comprising a plurality of rotor blades; a stationary component; a plurality of articulating seal members coupled to said stationary component; and a biasing mechanism comprising an actuation ring, said biasing mechanism coupled to said plurality of articulating seal members for use in selectively translating said plurality of articulating seal members when said actuation ring is rotated circumferentially relative to said stationary component.
 9. The turbine engine in accordance with claim 8, wherein said actuation ring is rotated in a first circumferential direction to translate said plurality of articulating seal members radially inward, and said actuation ring is rotated in a second circumferential direction to translate said plurality of articulating seal members radially outward.
 10. The turbine engine in accordance with claim 9, wherein a clearance between said plurality of articulating seal members and said plurality of rotor blades is selected based on a degree of rotation of said actuation ring in the first and second circumferential directions.
 11. The turbine engine in accordance with claim 8, wherein said biasing mechanism comprises at least one lever coupled between said actuation ring and at least one of said plurality of articulating seal members, wherein said at least one lever is configured to convert circumferential movement of said actuation ring into substantially linear movement of said plurality of articulating seal members.
 12. The turbine engine in accordance with claim 8 further comprising a slide track coupled to adjacent articulating seal members, said slide track configured to substantially maintain alignment between said adjacent articulating seal members as they selectively translate linearly.
 13. The turbine engine in accordance with claim 8, wherein said biasing mechanism comprises a biasing element coupled to at least one of said plurality of articulating seal members, said biasing element configured to ensure the selective translation of said at least one of said plurality of articulating seal members is responsive to the circumferential rotation of said actuation ring.
 14. The turbine engine in accordance with claim 8 further comprising a rack and pinion assembly associated with said actuation ring and configured to facilitate translating said plurality of articulating seal members in response to rotation of said actuation ring relative to said stationary component.
 15. A method of assembling a variable clearance mechanism for use in a turbine engine, said method comprising: providing a stationary component; coupling a plurality of articulating seal members to the stationary component; coupling an actuation ring to the plurality of articulating seal members such that the actuation ring is configured to selectively translate the plurality of articulating seal members when the actuation ring is rotated circumferentially relative to the stationary component.
 16. The method in accordance with claim 15, wherein coupling the actuation ring to the plurality of articulating seal members comprises coupling at least one lever between the actuation ring and the plurality of articulating seal members.
 17. The method in accordance with claim 16, wherein coupling at least one lever comprises coupling the at least one lever between the actuation ring and each of the plurality of articulating seal members such that the plurality of articulating seal members are simultaneously translated when the actuation ring is rotated circumferentially.
 18. The method in accordance with claim 16 further comprising forming a slot in at least one of the stationary component and the at least one lever, wherein the slot facilitates sliding engagement between the at least one lever and at least one of the actuation ring, the stationary component, and the plurality of articulating seal members.
 19. The method in accordance with claim 15 further comprising coupling an actuator to the actuation ring, wherein the actuator is configured to induce circumferential rotation to the actuation ring.
 20. The method in accordance with claim 15 further comprising defining a distance between the stationary component and the actuation ring that remains substantially uniform as the actuation ring rotates circumferentially. 